gl_rasterizer: add clipping plane z<=0 defined in PICA

src/video_core/renderer_opengl/gl_rasterizer.cpp

@@ -28,6 +28,9 @@ MICROPROFILE_DEFINE(OpenGL_Blits, "OpenGL", "Blits", MP_RGB(100, 100, 255));
 MICROPROFILE_DEFINE(OpenGL_CacheManagement, "OpenGL", "Cache Mgmt", MP_RGB(100, 255, 100));
 
 RasterizerOpenGL::RasterizerOpenGL() : shader_dirty(true) {
+    // Clipping plane 0 is always enabled for PICA fixed clip plane z <= 0
+    state.clip_distance[0] = true;
+
     // Create sampler objects
     for (size_t i = 0; i < texture_samplers.size(); ++i) {
         texture_samplers[i].Create();

src/video_core/renderer_opengl/gl_shader_gen.cpp

@@ -1196,6 +1196,8 @@ void main() {
     normquat = vert_normquat;
     view = vert_view;
     gl_Position = vec4(vert_position.x, vert_position.y, -vert_position.z, vert_position.w);
+    gl_ClipDistance[0] = -vert_position.z; // fixed PICA clipping plane z <= 0
+    // TODO (wwylele): calculate gl_ClipDistance[1] from user-defined clipping plane
 }
 )";
 

src/video_core/renderer_opengl/gl_state.cpp

@@ -68,6 +68,8 @@ OpenGLState::OpenGLState() {
     draw.vertex_buffer = 0;
     draw.uniform_buffer = 0;
     draw.shader_program = 0;
+
+    clip_distance = {};
 }
 
 void OpenGLState::Apply() const {
@@ -261,6 +263,17 @@ void OpenGLState::Apply() const {
         glUseProgram(draw.shader_program);
     }
 
+    // Clip distance
+    for (size_t i = 0; i < clip_distance.size(); ++i) {
+        if (clip_distance[i] != cur_state.clip_distance[i]) {
+            if (clip_distance[i]) {
+                glEnable(GL_CLIP_DISTANCE0 + i);
+            } else {
+                glDisable(GL_CLIP_DISTANCE0 + i);
+            }
+        }
+    }
+
     cur_state = *this;
 }
 

src/video_core/renderer_opengl/gl_state.h

@@ -4,6 +4,7 @@
 
 #pragma once
 
+#include <array>
 #include <glad/glad.h>
 
 namespace TextureUnits {
@@ -123,6 +124,8 @@ public:
         GLuint shader_program;   // GL_CURRENT_PROGRAM
     } draw;
 
+    std::array<bool, 2> clip_distance; // GL_CLIP_DISTANCE
+
     OpenGLState();
 
     /// Get the currently active OpenGL state